The ski bum of the iOS development community Kirby Turner wrote up how he using Auto Layout and was lucky enough to get a large audience for it through iOS Dev Weekly. I’m happy to see that Kirby is embracing Auto Layout. I did take issue with the premise of his article though: that he is writing all of his constraints in code rather than using Interface Builder.

It’s totally possible to do this, and there are situations where I do it as well. Small views with a few basic constraints are usually quicker and easier to write without a Xib. Insanely complex views such as the [TED video player] I wrote and maintain are also too heavy for a straight Xib implementation.

For pretty much any situation outside of that? You are doing yourself a disservice avoiding Interface Builder now that we are switching to using Auto Layout rather than springs and struts.

Why? Allow me to share a few reasons.

Instant Ambiguity and Conflict Checking

When you are defining the constraint-based relationships between your views in Interface Builder, you get real-time feedback in the Xib or Storyboard’s sidebar. If you see a yellow circle, there’s likely a misalignment. It’s a warning. If you see a red circle, there’s either a conflict, ambiguity, or some other issue that is going to cause pain when you build and run.

If you write all your constraints in code, you don’t find out about these sorts of issues until you run the application and get hit with an exception.

Code Is A Liability

The less code I have to manage, the better. Not only do Xibs and Storyboards let me visually lay out the main components of my interface, I can also define the attributes on them without having to type out more code. That’s something we have always had.

Now with Auto Layout, we can also define our constraints in the same Xib files rather than having to sprinkle bits of code all over our projects. Every line of code you write now is a line of code you have to manage six months from now. I’d rather have less management personally.

You Suck At Typing

One of Auto Layout’s best features is its ASCII syntax for defining multiple constraints quickly. There are legimitate times where you don’t want to or need to lay out your constraints in a Xib. It’s not without fault though.

Let’s say you want to lay out a constraint with NSLayoutConstraint‘s constraintsWithVisualFormat:options:metrics:views method. Everything you type into the constraintsWithVisualFormat section has zero checking of its syntax. It’s just yet another string literal to Xcode. The only way you will know that you screwed it up is to run the app and see what crashed.

Apple could theoretically fix this in the future, but as of Xcode 5.1 you have to be a perfect typist. I’m far from perfect.

Visual Layout

From a learning perspective, I truly believe the best way to begin to understand and use Auto Layout is through Interface Builder. I’m a visual learner, and being able to lay out my views and then see a visual representation of the constraint relationships between two views is killer for fully understanding what the new layout system is doing.

By writing everything in code, you are putting yourself behind the eight ball before you have even gotten started. I’d put money on the fact that most people that try Auto Layout and then ditch it either haven’t touched Interface Builder since Xcode 4 (which sucked) or are trying to do all their Auto Layout work in code.

Summary

Interface Builder’s Auto Layout support isn’t perfect. There’s plenty of things I’d love to see Apple change, but writing all your constraints in code only should be the exception, not the norm.